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EDITORIAL
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Correspondence address:
Correspondence address:
Correspondence address:
Correspondence address:
Correspondence address: Monika Franczuk, MD, PhD, Lung Function Department, Institute of Tuberculosis and Lung Diseases in Warsaw, Płocka 26 St., 01–138 Warszawa, e-mail: m.franczuk@igichp.edu.pl
Date of paper receipt at the editorial office: 14 Sept 2011. Copyright © 2011 Via Medica ISSN 0867-7077
Monika Franczuk
Lung Function Department, Institute of Tuberculosis and Lung Diseases in Warsaw Head: Prof. S. Wesołowski, MD, PhD
Recognition of exercise-induced bronchoconstriction — a task for a medal
Rozpoznawanie powysiłkowego skurczu oskrzeli — zadanie na medal
Pneumonol. Alergol. Pol. 2011; 79, 6: 379-381
A physiological response to exercise leads to increased ventilation, which is an adaptive mecha- nism related to increased body demand for oxygen and accelerated metabolism. Maintaining constant blood gasometry parameters is the main task of the breathing control system. Increased respiratory drive and intensified activity of respiratory musc- les lead to increased tidal volume. During strenu- ous physical exercise, when this volume reaches the level of approximately 70-75% of total lung capacity, breathing frequency is also significantly higher. In poorly trained individuals, intense bre- athing may be interpreted as a pathological symp- tom, dyspnoea, especially if it impairs normal func- tioning and causes respiratory discomfort and con- siderable fatigue. On the other hand, diseases of the respiratory system such as chronic obstructi- ve pulmonary disease or pulmonary fibrosis are accompanied by impaired exercise tolerance, re- sulting in the need to reduce the intensity of ef- fort. These are immanent features of disease pro- gression and impaired lung function.
A specific clinical situation is the occurrence of dyspnoea and respiratory symptoms during or after strenuous physical exercise. Exercise-indu- ced bronchoconstriction (EIB) is a term for tran- sient constriction of the airways leading to impa- ired air flow and symptoms such as cough, whe- ezing, or dyspnoea, which appear during strenu- ous physical exercise or, more frequently, after its
discontinuation. A delayed reaction, which occurs less often, refers to a bronchospasm that appears 3 to 8 hours after exercise. The pathogenesis of this phenomenon is not fully understood. Intense exer- tion and increased ventilation cause water loss and increased osmolarity of airway mucus [1]. Thro- ugh the activation of mast cells, epithelial cells, eosinophils, stimulation of nervous endings, and release of numerous inflammatory mediators, histamine, prostaglandins, or leukotrienes it results in constriction of bronchial smooth muscle, mu- cosal oedema, and increased vascular permeabili- ty. According to another theory, called thermic or vascular, the main role is played by exposure to cool air, which contributes to vasoconstriction pre- venting heat loss. Discontinuation of exercise and reduction of ventilation cause vasodilation, con- gestion, and mucosal oedema, resulting in narro- wing of the bronchi and restricted air flow. It se- ems that exercise-induced bronchoconstriction is a result of both mechanisms.
Exercise-induced bronchoconstriction may occur in patients with diagnosed asthma; up to 90% of patients report exercise-induced symptoms [2]. It usually indicates insufficient disease control and the necessity of treatment modification. Exer- cise-induced bronchoconstriction also affects 10- 15% of the general population, including indivi- duals without a history of asthma or atopy. EIB is significantly more frequent in sportsmen, especial-
Pneumonologia i Alergologia Polska 2011, vol. 79, no 6, pages 379–381
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authors investigated the issue of evaluating the usefulness of selected tests for EIB diagnosis.
They methodically designed a study that inclu- ded patients suffering from asthma, individuals reporting EIB symptoms, and healthy volunteers.
The study protocol included: assessment of lung function, bronchial challenge test to methacho- line and adenosine monophosphate (AMP), and exercise challenge tests. It was demonstrated that for the diagnosis of EIB the most valuable was a combination of typical symptoms (dyspnea, co- ugh and wheezing after exercise) with positive results of AMP challenge test. The achieved re- sults, characterised by high specificity (94%) and sensitivity (70%), may indicate a very promising diagnostic option for EIB, especially for patients reporting EIB symptoms without atopy or diagno- sed asthma in anamnesis, in whom initiation of appropriate treatment may lead to significant im- provement of quality of life and normal functio- ning.
The problem of exercise-induced bronchocon- striction, sometimes also called exercise induced asthma (EIA), has been known and investigated for several years. From time to time, especially in con- nection with international sports events, this issue is raised and becomes the subject of numerous di- scussions and controversies. Considerations are mainly focused on athletes with diagnosis of exer- cise-induced asthma, who are treated and achieve great results, confirmed by sporting awards. Many debates also concern the role of implemented tre- atment as a doping agent. On the other hand, epi- demiological studies have demonstrated that EIB is one of the most important risk factors for sud- den death in young professional sportsmen [11].
It has been pointed out that routine health asses- sment in sportsmen should include not only the cardio-vascular system, but also the respiratory system, with special focus on diagnosing asthma and EIB. It is also very important that the teams taking care of athletes, i.e. coaches, instructors, and sports medicine doctors, should be aware of the higher risk of EIB in professional sportsmen prac- tising „asthmogenic” disciplines (especially win- ter sports), and its possible symptoms and diagno- stic tools.
Therefore, it is very important to precisely prepare and consequently follow diagnostic crite- ria for EIB, and to establish indications for its phar- macotherapy.. The importance of the AMP chal- lenge test, as described in the results of Hildebrand et al. [10], might be very useful; therefore, such studies should be continued and confirmed in lar- ger groups of subjects.
ly professionals taking part in competitive sports like cycling, long-distance running, swimming, and winter sports such as cross-country skiing or speed skating. Among these athletes, EIB symptoms have been observed in 50-70% of individuals [3-6]. A review of the results of recently published studies indicates that EIB mechanism in this population may also be related to alternating processes of da- mage and repair in the bronchial epithelium, indu- ced by repeated hyperventilation and increased exposure to dry, cool, and polluted air [7].
The literature and guidelines regarding EIB treatment emphasize the role of proper diagnosis.
The data from anamnesis, based on symptoms re- ported by the patients, have been considered as definitely insufficient for diagnosis and inappropria- te for initiation of treatment [8]. It has also been emphasized that, due to mechanisms contributing to EIB that are slightly different than those in asth- matic patients, non-specific provocation tests with histamine or methacholine have a limited diagno- stic value. Despite numerous studies, it has not been clearly established which method would show the features of a „gold standard” in diagnosing EIB.
The currently recommended method of dia- gnosing EIB, accepted and required by the Inter- national Olympic Committee and World Anti-Do- ping Agency, is exercise challenge testing. It sho- uld be noted that it is not equivalent to the stair climbing test or 6-minute-walk test used in diagno- sing and monitoring respiratory diseases. It is re- quired that exercise challenge tests be performed under specific, controlled conditions. Protocols of recommended exercise tests have been discribed in detail by Hildebrand [7]. Diagnosis is based on the presence of bronchial obstruction induced by the stimulus, and decreased forced expiratory vo- lume in 1 second (FEV1) by at least 10% in rela- tion to the baseline values.
An exercise challenge test, performed under the recommended conditions, is not commonly used due to costs and limited access to adequate equipment. Thus, other methods for diagnosing EIB are being considered, including eucapnic vo- luntary hyperventilation, mannitol challenge test, or exposure to hyper- and hypotonic aerosols.
Other studies, also carried out by Polish investi- gators [9], are aimed at including into EIB diagno- stics the measurement of nitric oxide concentra- tion in exhaled air (FENO) or the evaluation of the concentration of eosinophil chemotactic agents in exhaled breath condensate (EBC).
In view of the above mentioned issues, the study carried out by Hildebrand et al. [10] has aro- used a great deal of interest and appreciation. The
Monika Franczuk, Recognition of exercise-induced bronchoconstriction — a task for a medal
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